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Log in to Facebook Developer Center (https://developers.facebook.com/ ).
Click MyApps -> Add a New App.
Enter the name of the app you want to use and click the Create New Facebook App Id button.
Select the platform you want to register.
After entering the necessary information on the quick start screen, register the app.
Android
Scroll down and enter the package name and default activity class name of your app and click the 'Next' button.After registering the key hash, click the 'Next' button to complete the registration.
IOS
Scroll down and enter the bundle ID. Enter the bundle ID and click 'Next' button to complete the registration.
Go to the app information page by clicking the MyApps -> Registered app name button in the top menu.
Check and save the displayed AppId and AppSecret.